The present invention relates generally to the field of electroplating or electroforming, and more particularly, is directed to the electrodeposition of karat gold upon a disposable substrate.
The process of electroplating is well known and consists generally of passing a direct electrical current through a solution or bath between two electrically conducting materials or poles which are placed in the solution at the positive and negative terminals of the direct current circuit. Electroforming is an electroplating process which utilizes special plating baths and which has been employed by prior workers in the art to produce an exact metallic reproduction of a model or substrate by forming thereon a relatively thick deposit of metal from the bath. The substrate may or may not be removed as required by the final commercial product, such as a master record or an article of jewelry. Electroforming has been successfully utilized by prior workers in the art to form relatively large pieces of gold jewelry at greatly reduced prices, when considering the size of the piece and the cost of a comparatively sized solid gold object. By employing a disposable substrate as a model and then plating pure gold over the model, there was thereby formed a hollow, configured, gold product which required considerably less gold than would otherwise be required when fabricating the piece by utilizing conventional gold working techniques.
When employing a substrate or model of non-conductive material, such as wax or expanded polystyrene, the model surfaces first had to be rendered electroconductive before the surfaces could be electroformed. In order to accomplish this, prior workers in the art have usually selected a solution containing a conductive metal and they sprayed, dipped or painted it over those surfaces of the model selected for electroforming. In one known technique, a model was first placed in a copper depositing solution or bath by attaching the model to the cathode by a copper wire and then immersing it in the electroplating bath to produce the formation of a film of copper over the substrate of sufficient thickness to form a suitable, conductive base for deposit of a noble metal, for example metallic silver or metallic gold. After cleaning by rinsing, the copper coated mandrel or substrate was placed in a silver or gold plating bath until the desired final thickness of silver or pure gold was formed in the exact configuration of the model. After electroforming the desired thickness of metallic silver or gold, the piece was then removed from the bath and the substrate material was then removed by employing suitable, known methods.
In order to produce gold electroforms, the prior workers in the art have usually employed a hot gold cyanide bath or electrolyte comprising a solution of gold, potassium or sodium cyanide, and dipotassium or disodium phosphate. The bath preferably was heated to 160.degree.-180.degree. F., and a current density between 1 to 5 amperes per square foot was employed. When thick gold deposits were desired, a greater percentage of gold in the bath was employed since this permits higher current densities and higher cathode efficiencies. It was found that higher temperatures and increased bath agitation could be employed to favor higher plating speeds.
The prior art electroforming techniques and procedures have generally proved acceptable to produce fine gold-veneered and silver jewelry and other commercial articles of precisely controlled configuration. When using the prior art gold electroforming techniques, the deposited gold was substantially twenty-four karat gold, a desirable product that could be mechanically formed or otherwise treated, such as by gold soldering. However, the final product was expensive and because of its purity, was quite soft.
In the past such techniques were generally successful and any gold products resulting from the known processes were considered to be uniquely formed, light of weight and of great merit. However, due to the ever increasing cost of gold, the need remains to develop a process that is capable of producing gold articles of acceptable size and quality, but which require even smaller quantities of pure gold. The existing procedures have never successfully been adapted to produce an acceptable karat gold electroform and all previous attempts resulted in gold deposits that failed either due to brittleness and/or through failure to build up the required thickness of deposit. Research has disclosed that there are no existing processes presently available for creating commercially acceptable, relatively thick, karat gold electroforms. The term "thick" karat gold electroform as utilized herein, is defined to mean a thickness of approximately 0.007 inches (0.013 cm.) or greater.